In general, a gas turbine engine operates in an extremely harsh environment characterized by very high temperatures, temperature gradients, and vibrations. A gas turbine engine typically includes a compressor for compressing an incoming flow of air, one or more combustors for mixing the compressed air with a flow of fuel and igniting the air/fuel mixture, and a turbine to drive the compressor and an external load such as an electrical generator. The combustors and other parts of the inner turbine shell are subject to extremely high temperatures from the combustion gases. An impingement sleeve assembly comprising impingement sleeve panels is therefore generally used to direct cooling air to hot regions of the outside diameter of the inner turbine shell. The impingement sleeve assembly may include perimeter skirts, which are typically welded onto the perimeter of each impingement sleeve panel. The perimeter skirts, in turn, fit into perimeter sealing grooves in the inner turbine shell. Each of the impingement sleeve panels is then typically bolted to the inner turbine shell, thereby forming the impingement sleeve assembly.
The impingement sleeve panels are typically a relatively thin material, and as a consequence, may have a tendency to expand or contract upon heating and cooling, respectively, at a faster rate than the inner turbine shell, to which they are fastened. This can result in transient sleeve stress, fatigue to the impingement sleeve panels, and shortened impingement sleeve life. Additionally, it may be difficult, even with a torque wrench, to torque down on the bolts used to fasten the impingement sleeve panels to the inner turbine shell with a reliable, repeatable degree of torque and consequent load along the axis of the bolts.
There is therefore a desire to provide a fastening system for fastening an impingement sleeve assembly to the inner turbine shell that allows for transient differential growth of the impingement sleeve assembly, while keeping the impingement sleeve assembly positively loaded for high cycle fatigue and model tuning. There is further a desire to provide a fastening system that can provide consistent impingement sleeve load input to allow for transient sliding of the impingement sleeve assembly and deterministic load along the axis of the fastening system.